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compress numerical expressions (#1513)

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safe operations
- `a === b` => `a == b`
- `a + -b`  => `a - b`
- `-a + b`  => `b - a`
- `a+ +b`   => `+b+a`

associative operations
(bit-wise operations are safe, otherwise `unsafe_math`)
- `a + (b + c)`       => `(a + b) + c`
- `(n + 2) + 3`       => `5 + n`
- `(2 * n) * 3`       => `6 * n`
- `(a | 1) | (2 | d)` => `(3 | a) | b`

fixes #412
This commit is contained in:
Alex Lam S.L
2017-03-03 18:04:32 +08:00
committed by GitHub
parent b5e0e8c203
commit 18059cc94f
3 changed files with 303 additions and 7 deletions
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136
test/compress/numbers.js
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@@ -17,3 +17,139 @@ hex_numbers_in_parentheses_for_prototype_functions: {
}
expect_exact: "-2;(-2).toFixed(0);2;2..toFixed(0);.2;.2.toFixed(0);2e-8;2e-8.toFixed(0);0xde0b6b3a7640080;(0xde0b6b3a7640080).toFixed(0);"
}
comparisons: {
options = {
comparisons: true,
}
input: {
console.log(
~x === 42,
x % n === 42
);
}
expect: {
console.log(
42 == ~x,
x % n == 42
);
}
}
evaluate_1: {
options = {
evaluate: true,
unsafe_math: false,
}
input: {
console.log(
x + 1 + 2,
x * 1 * 2,
+x + 1 + 2,
1 + x + 2 + 3,
1 | x | 2 | 3,
1 + x-- + 2 + 3,
1 + (x*y + 2) + 3,
1 + (2 + x + 3),
1 + (2 + ~x + 3),
-y + (2 + ~x + 3),
1 & (2 & x & 3),
1 + (2 + (x |= 0) + 3)
);
}
expect: {
console.log(
x + 1 + 2,
1 * x * 2,
+x + 1 + 2,
1 + x + 2 + 3,
3 | x,
1 + x-- + 2 + 3,
x*y + 2 + 1 + 3,
1 + (2 + x + 3),
2 + ~x + 3 + 1,
-y + (2 + ~x + 3),
0 & x,
2 + (x |= 0) + 3 + 1
);
}
}
evaluate_2: {
options = {
evaluate: true,
unsafe_math: true,
}
input: {
console.log(
x + 1 + 2,
x * 1 * 2,
+x + 1 + 2,
1 + x + 2 + 3,
1 | x | 2 | 3,
1 + x-- + 2 + 3,
1 + (x*y + 2) + 3,
1 + (2 + x + 3),
1 & (2 & x & 3),
1 + (2 + (x |= 0) + 3)
);
}
expect: {
console.log(
x + 1 + 2,
2 * x,
3 + +x,
1 + x + 2 + 3,
3 | x,
6 + x--,
6 + x*y,
1 + (2 + x + 3),
0 & x,
6 + (x |= 0)
);
}
}
evaluate_3: {
options = {
evaluate: true,
unsafe: true,
unsafe_math: true,
}
input: {
console.log(1 + Number(x) + 2);
}
expect: {
console.log(3 + +x);
}
}
evaluate_4: {
options = {
evaluate: true,
}
input: {
console.log(
1+ +a,
+a+1,
1+-a,
-a+1,
+a+ +b,
+a+-b,
-a+ +b,
-a+-b
);
}
expect: {
console.log(
+a+1,
+a+1,
1-a,
1-a,
+a+ +b,
+a-b,
-a+ +b,
-a-b
);
}
}