field: Document return value of fe_sqrt() #1347

pull real-or-random wants to merge 1 commits into bitcoin-core:master from real-or-random:202306-fe-sqrt-ret-docs changing 1 files +4 −2

real-or-random commented at 9:50 AM on June 15, 2023: contributor

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real-or-random added the label documentation on Jun 15, 2023
real-or-random commented at 9:51 AM on June 15, 2023: contributor

@stratospher Interested in reviewing this small PR?

in src/field.h:271 in c66c30cd57 outdated

 266 | @@ -267,8 +267,10 @@ static void secp256k1_fe_sqr(secp256k1_fe *r, const secp256k1_fe *a);
 267 |  /** Compute a square root of a field element.
 268 |   *
 269 |   * On input, a must be a valid field element with magnitude<=8; r need not be initialized.
 270 | - * Performs {r = sqrt(a)} or {r = sqrt(-a)}, whichever exists. The resulting value
 271 | - * represented by r will be a square itself. Variables r and a must not point to the same object.
 272 | + * Performs {r = sqrt(a)} and returns 1 if sqrt(a) exists.
 273 | + * Performs {r = sqrt(-a) and returns 0 otherwise; then sqrt(-a) exists.

stratospher commented at 3:21 PM on June 15, 2023:

c66c30c: nit

 * Performs {r = sqrt(-a)} and returns 0 otherwise; then sqrt(-a) exists.

stratospher commented at 3:21 PM on June 15, 2023: contributor

ACK c66c30c.
real-or-random force-pushed on Jun 15, 2023
stratospher commented at 3:26 PM on June 15, 2023: contributor

ACK cc1ad2f.

in src/field.h:271 in cc1ad2f97e outdated

 266 | @@ -267,8 +267,10 @@ static void secp256k1_fe_sqr(secp256k1_fe *r, const secp256k1_fe *a);
 267 |  /** Compute a square root of a field element.
 268 |   *
 269 |   * On input, a must be a valid field element with magnitude<=8; r need not be initialized.
 270 | - * Performs {r = sqrt(a)} or {r = sqrt(-a)}, whichever exists. The resulting value
 271 | - * represented by r will be a square itself. Variables r and a must not point to the same object.
 272 | + * Performs {r = sqrt(a)} and returns 1 if sqrt(a) exists.
 273 | + * Performs {r = sqrt(-a)} and returns 0 otherwise; then sqrt(-a) exists.

jonasnick commented at 3:22 PM on June 16, 2023:

nit: maybe case distinction like this is clearer?

 * If sqrt(a) exists, performs {r = sqrt(a)} and returns 1.
 * Otherwise, sqrt(-a) exists. The function performs {r = sqrt(-a)} and returns 0.

real-or-random commented at 10:19 PM on June 20, 2023:

Done.

field: Document return value of fe_sqrt()
Co-authored-by: Jonas Nick <jonasd.nick@gmail.com>
5779137457
real-or-random force-pushed on Jun 20, 2023
sipa commented at 11:45 PM on June 20, 2023: contributor

ACK 57791374579595bbc5d8d2e55f7fa0bc40d861a4
theStack approved
theStack commented at 3:30 PM on June 21, 2023: contributor

ACK 57791374579595bbc5d8d2e55f7fa0bc40d861a4
real-or-random merged this on Jun 21, 2023
real-or-random closed this on Jun 21, 2023
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