23 lines
736 B
D
23 lines
736 B
D
import std.stdio, std.range, std.traits;
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/// Approximates y(t) in y'(t)=f(t,y) with y(a)=y0 and t=a..b and the step size h.
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void euler(F)(in F f, in double y0, in double a, in double b, in double h) @safe
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if (isCallable!F && __traits(compiles, { real r = f(0.0, 0.0); })) {
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double y = y0;
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foreach (immutable t; iota(a, b, h)) {
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writefln("%.3f %.3f", t, y);
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y += h * f(t, y);
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}
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"done".writeln;
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}
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void main() {
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/// Example: Newton's cooling law.
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enum newtonCoolingLaw = (in double time, in double t)
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pure nothrow @safe @nogc => -0.07 * (t - 20);
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euler(newtonCoolingLaw, 100, 0, 100, 2);
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euler(newtonCoolingLaw, 100, 0, 100, 5);
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euler(newtonCoolingLaw, 100, 0, 100, 10);
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}
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