eval 0.4.3

Expression evaluator
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


use {Function, Functions, Context, Contexts, Compiled, Value};
use tree::Tree;
use error::Error;
use serde::Serialize;
use to_value;
use std::fmt;


/// Expression builder
pub struct Expr {
    expression: String,
    compiled: Option<Compiled>,
    functions: Functions,
    contexts: Contexts,
}

impl Expr {
    /// Create an expression.
    pub fn new<T: Into<String>>(expr: T) -> Expr {
        Expr {
            expression: expr.into(),
            compiled: None,
            functions: Functions::new(),
            contexts: create_empty_contexts(),
        }
    }

    /// Set function.
    pub fn function<T, F>(mut self, name: T, function: F) -> Expr
        where T: Into<String>,
              F: 'static + Fn(Vec<Value>) -> Result<Value, Error> + Sync + Send
    {
        self.functions.insert(name.into(), Function::new(function));
        self
    }

    /// Set value.
    pub fn value<T, V>(mut self, name: T, value: V) -> Expr
        where T: Into<String>,
              V: Serialize
    {
        self.contexts.last_mut().unwrap().insert(name.into(), to_value(value));
        self
    }

    /// Compile an expression.
    /// An expression can be compiled only once and then invoked multiple times with different context and function.
    /// You can also execute a expression without compile.
    pub fn compile(mut self) -> Result<Expr, Error> {
        self.compiled = Some(Tree::new(self.expression.clone()).compile()?);
        Ok(self)
    }

    /// Execute the expression.
    pub fn exec(&self) -> Result<Value, Error> {
        if self.compiled.is_none() {
            Tree::new(self.expression.clone()).compile()?(&self.contexts, &self.functions)
        } else {
            self.compiled.as_ref().unwrap()(&self.contexts, &self.functions)
        }
    }

    fn get_compiled(&self) -> Option<&Compiled> {
        self.compiled.as_ref()
    }
}

impl Clone for Expr {
    /// Returns a copy of the value. Notice that functions can not be cloned. The cloned expr's functions will be empty.
    fn clone(&self) -> Expr {
        Expr {
            expression: self.expression.clone(),
            compiled: if self.compiled.is_some() {
                Some(Tree::new(self.expression.clone()).compile().unwrap())
            } else {
                None
            },
            contexts: self.contexts.clone(),
            functions: Functions::new(),
        }
    }
}

impl fmt::Debug for Expr {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(formatter, "{:?}", self.expression)
    }
}


/// Execute options
pub struct ExecOptions<'a> {
    expr: &'a Expr,
    contexts: Option<&'a [Context]>,
    functions: Option<&'a Functions>,
}

impl<'a> ExecOptions<'a> {
    /// Create an option.
    pub fn new(expr: &'a Expr) -> ExecOptions<'a> {
        ExecOptions {
            expr: expr,
            contexts: None,
            functions: None,
        }
    }

    /// Set contexts.
    pub fn contexts(&mut self, contexts: &'a [Context]) -> &'a mut ExecOptions {
        self.contexts = Some(contexts);
        self
    }

    /// Set functions.
    pub fn functions(&mut self, functions: &'a Functions) -> &'a mut ExecOptions {
        self.functions = Some(functions);
        self
    }

    /// Execute the compiled expression.
    pub fn exec(&self) -> Result<Value, Error> {
        let empty_contexts = create_empty_contexts();
        let empty_functions = Functions::new();

        let contexts = if self.contexts.is_some() {
            self.contexts.unwrap()
        } else {
            &empty_contexts
        };

        let functions = if self.functions.is_some() {
            self.functions.unwrap()
        } else {
            &empty_functions
        };

        let compiled = self.expr.get_compiled();
        if compiled.is_none() {
            Tree::new(self.expr.expression.clone()).compile()?(contexts, functions)
        } else {
            compiled.unwrap()(contexts, functions)
        }
    }
}


fn create_empty_contexts() -> Contexts {
    let mut contexts = Contexts::new();
    contexts.push(Context::new());
    contexts
}