rmathlib 1.1.0

A Rust Port of R's C Library of Special Functions
Documentation 
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use crate::nmath::*;
use crate::rmath::*;

/// Calculates the cosine of a number given in multiples of π (pi).
pub fn cospi(mut x: f64) -> f64 {
    if x.is_nan() {
        return x;
    }
    if !r_finite(x) {
        ml_warn_return_nan();
    }

    x = x.abs() % 2.0;
    if x % 1.0 == 0.5 {
        return 0.;
    };
    if x == 1. {
        return -1.;
    };
    if x == 0. {
        return 1.;
    };
    (M_PI * x).cos()
}

/// Calculates the sinus of a number given in multiples of π (pi).
pub fn sinpi(mut x: f64) -> f64 {
    if x.is_nan() {
        return x;
    }
    if !r_finite(x) {
        ml_warn_return_nan();
    }

    x %= 2.0;
    if x <= -1.0 {
        x += 2.0;
    } else if x > 1.0 {
        x -= 2.0;
    }
    if x == 0.0 || x == 1.0 {
        return 0.0;
    }
    if x == 0.5 {
        return 1.0;
    }
    if x == -0.5 {
        return -1.0;
    }
    (M_PI * x).sin()
}

/// Calculates the tangent of a number given in multiples of π (pi).
pub fn tanpi(mut x: f64) -> f64 {
    if x.is_nan() {
        return x;
    }
    if !r_finite(x) {
        ml_warn_return_nan();
    }

    x %= 1.0;
    if x <= -0.5 {
        x += 1.0;
    } else if x > 0.5 {
        x -= 1.0;
    }

    if x == 0.0 {
        0.0
    } else if x == 0.5 {
        ML_NAN
    } else if x == 0.25 {
        1.0
    } else if x == -0.25 {
        -1.0
    } else {
        (M_PI * x).tan()
    }
}