seq-runtime 5.6.1

Runtime library for the Seq programming language
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247

use super::*;
use crate::stack::push;

// Helper: predicate that always returns true (keeps value, pushes true)
// Stack effect: ( value -- value Bool )
unsafe extern "C" fn pred_always_true(stack: Stack) -> Stack {
    unsafe { push(stack, Value::Bool(true)) }
}

// Helper: predicate that always returns false (keeps value, pushes false)
// Stack effect: ( value -- value Bool )
unsafe extern "C" fn pred_always_false(stack: Stack) -> Stack {
    unsafe { push(stack, Value::Bool(false)) }
}

// Helper: predicate that checks if top value is zero
// Stack effect: ( Int -- Int Bool )
unsafe extern "C" fn pred_is_zero(stack: Stack) -> Stack {
    unsafe {
        let val = crate::stack::peek(stack);
        match val {
            Value::Int(n) => push(stack, Value::Bool(n == 0)),
            _ => panic!("pred_is_zero: expected Int"),
        }
    }
}

// Helper: predicate that checks if value is negative
// Stack effect: ( Int -- Int Bool )
unsafe extern "C" fn pred_is_negative(stack: Stack) -> Stack {
    unsafe {
        let val = crate::stack::peek(stack);
        match val {
            Value::Int(n) => push(stack, Value::Bool(n < 0)),
            _ => panic!("pred_is_negative: expected Int"),
        }
    }
}

// Helper: body that drops value and pushes "matched"
// Stack effect: ( value -- String )
unsafe extern "C" fn body_matched(stack: Stack) -> Stack {
    unsafe {
        let (stack, _) = pop(stack);
        push(
            stack,
            Value::String(crate::seqstring::global_string("matched".to_string())),
        )
    }
}

// Helper: body that drops value and pushes "zero"
// Stack effect: ( value -- String )
unsafe extern "C" fn body_zero(stack: Stack) -> Stack {
    unsafe {
        let (stack, _) = pop(stack);
        push(
            stack,
            Value::String(crate::seqstring::global_string("zero".to_string())),
        )
    }
}

// Helper: body that drops value and pushes "positive"
// Stack effect: ( value -- String )
unsafe extern "C" fn body_positive(stack: Stack) -> Stack {
    unsafe {
        let (stack, _) = pop(stack);
        push(
            stack,
            Value::String(crate::seqstring::global_string("positive".to_string())),
        )
    }
}

// Helper: body that drops value and pushes "negative"
// Stack effect: ( value -- String )
unsafe extern "C" fn body_negative(stack: Stack) -> Stack {
    unsafe {
        let (stack, _) = pop(stack);
        push(
            stack,
            Value::String(crate::seqstring::global_string("negative".to_string())),
        )
    }
}

// Helper: body that drops value and pushes "default"
// Stack effect: ( value -- String )
unsafe extern "C" fn body_default(stack: Stack) -> Stack {
    unsafe {
        let (stack, _) = pop(stack);
        push(
            stack,
            Value::String(crate::seqstring::global_string("default".to_string())),
        )
    }
}

// Helper to create a quotation value from a function pointer
fn make_quotation(f: unsafe extern "C" fn(Stack) -> Stack) -> Value {
    let ptr = f as *const () as usize;
    Value::Quotation {
        wrapper: ptr,
        impl_: ptr,
    }
}

#[test]
fn test_cond_single_match() {
    // Test: single predicate that always matches
    // Stack: value [pred_always_true] [body_matched] 1
    unsafe {
        let stack = crate::stack::alloc_test_stack();
        let stack = push(stack, Value::Int(42)); // value
        let stack = push(stack, make_quotation(pred_always_true));
        let stack = push(stack, make_quotation(body_matched));
        let stack = push(stack, Value::Int(1)); // count

        let stack = cond(stack);

        let (_, result) = pop(stack);
        match result {
            Value::String(s) => assert_eq!(s.as_str(), "matched"),
            _ => panic!("Expected String, got {:?}", result),
        }
    }
}

#[test]
fn test_cond_first_match_wins() {
    // Test: multiple predicates, first one that matches should win
    // Both predicates would match, but first one should be used
    // Stack: value [pred_always_true] [body_matched] [pred_always_true] [body_default] 2
    unsafe {
        let stack = crate::stack::alloc_test_stack();
        let stack = push(stack, Value::Int(42)); // value
        let stack = push(stack, make_quotation(pred_always_true));
        let stack = push(stack, make_quotation(body_matched)); // first pair
        let stack = push(stack, make_quotation(pred_always_true));
        let stack = push(stack, make_quotation(body_default)); // second pair
        let stack = push(stack, Value::Int(2)); // count

        let stack = cond(stack);

        let (_, result) = pop(stack);
        match result {
            Value::String(s) => assert_eq!(s.as_str(), "matched"), // first body wins
            _ => panic!("Expected String, got {:?}", result),
        }
    }
}

#[test]
fn test_cond_second_match() {
    // Test: first predicate fails, second matches
    // Stack: value [pred_always_false] [body_matched] [pred_always_true] [body_default] 2
    unsafe {
        let stack = crate::stack::alloc_test_stack();
        let stack = push(stack, Value::Int(42)); // value
        let stack = push(stack, make_quotation(pred_always_false));
        let stack = push(stack, make_quotation(body_matched)); // first pair - won't match
        let stack = push(stack, make_quotation(pred_always_true));
        let stack = push(stack, make_quotation(body_default)); // second pair - will match
        let stack = push(stack, Value::Int(2)); // count

        let stack = cond(stack);

        let (_, result) = pop(stack);
        match result {
            Value::String(s) => assert_eq!(s.as_str(), "default"), // second body wins
            _ => panic!("Expected String, got {:?}", result),
        }
    }
}

#[test]
fn test_cond_classify_number() {
    // Test: classify numbers as negative, zero, or positive
    // This mimics the example from the docs
    unsafe {
        // Test negative number
        let stack = crate::stack::alloc_test_stack();
        let stack = push(stack, Value::Int(-5)); // value
        let stack = push(stack, make_quotation(pred_is_negative));
        let stack = push(stack, make_quotation(body_negative));
        let stack = push(stack, make_quotation(pred_is_zero));
        let stack = push(stack, make_quotation(body_zero));
        let stack = push(stack, make_quotation(pred_always_true)); // default
        let stack = push(stack, make_quotation(body_positive));
        let stack = push(stack, Value::Int(3)); // count

        let stack = cond(stack);
        let (_, result) = pop(stack);
        match result {
            Value::String(s) => assert_eq!(s.as_str(), "negative"),
            _ => panic!("Expected String"),
        }

        // Test zero
        let stack = crate::stack::alloc_test_stack();
        let stack = push(stack, Value::Int(0)); // value
        let stack = push(stack, make_quotation(pred_is_negative));
        let stack = push(stack, make_quotation(body_negative));
        let stack = push(stack, make_quotation(pred_is_zero));
        let stack = push(stack, make_quotation(body_zero));
        let stack = push(stack, make_quotation(pred_always_true)); // default
        let stack = push(stack, make_quotation(body_positive));
        let stack = push(stack, Value::Int(3)); // count

        let stack = cond(stack);
        let (_, result) = pop(stack);
        match result {
            Value::String(s) => assert_eq!(s.as_str(), "zero"),
            _ => panic!("Expected String"),
        }

        // Test positive
        let stack = crate::stack::alloc_test_stack();
        let stack = push(stack, Value::Int(42)); // value
        let stack = push(stack, make_quotation(pred_is_negative));
        let stack = push(stack, make_quotation(body_negative));
        let stack = push(stack, make_quotation(pred_is_zero));
        let stack = push(stack, make_quotation(body_zero));
        let stack = push(stack, make_quotation(pred_always_true)); // default
        let stack = push(stack, make_quotation(body_positive));
        let stack = push(stack, Value::Int(3)); // count

        let stack = cond(stack);
        let (_, result) = pop(stack);
        match result {
            Value::String(s) => assert_eq!(s.as_str(), "positive"),
            _ => panic!("Expected String"),
        }
    }
}

// Note: #[should_panic] tests don't work with extern "C" functions because
// they can't unwind. The following panic conditions are documented in the
// function's doc comments and verified by the compiler's type system:
//
// - "cond: no predicate matched" - when all predicates return false
// - "cond: need at least one predicate/body pair" - when count is 0
// - "cond: count must be non-negative" - when count is negative
// - "cond: expected body Quotation" - when body is not a Quotation
// - "cond: expected predicate Quotation" - when predicate is not a Quotation
// - "cond: predicate must return Bool" - when predicate returns non-Bool