gofor

Because who can resist a good homonym?

What is it?

gofor analyzes the types of for loops encountered in Go code. It is geared towards detecting counting loops -- loops of the form for i := min; i < max; i += stride -- and its categorizations are mostly steps on the way to ruling out non-counting loops and then detecting interesting types of counting loops -- special values for min and stride (0 and 1 respectively) and literal vs non-literal min/max/stride.

It is intended to be used in conjunction with sort and uniq.

Running this on all the packages that were go gettable from http://godoc.org/-/index as of Sep 25, 2013, yielded the following counts. (Results accounting for > 1% are annotated for clarity. Beyond that, use the source, Luke.)

101238 range: for ?? := range ?? {
31705 counting loop min 0, max non-literal, stride 1: for i := 0; i < ??; i++ {
14508 bare for: for {
12814 cond only: for ?? {
7235 cond not < or <=: for ??; not LT[E]; ?? {
5472 counting loop min 0, max literal, stride 1: for i := 0; i < N; i++ {
4616 counting loop min non-literal, max non-literal, stride 1: for i := ??; i < ??; i++ {
1728 missing init
1535 counting loop min literal, max non-literal, stride 1
1508 missing post
 908 counting loop min literal, max literal, stride 1
 671 counting loop min non-literal, max literal, stride 1
 605 init multiple values
 554 counting loop min 0, max non-literal, stride literal
 236 cond lhs not identifier
 236 counting loop min 0, max non-literal, stride non-literal
 227 post assign not += or -= (but might be i = i - 1, oh well)
 191 counting loop min 0, max literal, stride literal
 162 counting loop min non-literal, max non-literal, stride non-literal
 103 counting loop min non-literal, max non-literal, stride literal
  89 counting loop min literal, max literal, stride literal
  78 counting loop min literal, max non-literal, stride literal
  76 init lhs != cond lhs
  59 counting loop min non-literal, max literal, stride literal
  26 post assign multiple values
  19 counting loop min literal, max non-literal, stride non-literal
  17 init not i := n
  15 counting loop min literal, max literal, stride non-literal
  13 init lhs != post incdec lhs
   6 counting loop min 0, max literal, stride non-literal
   4 counting loop min non-literal, max literal, stride non-literal
   3 init lhs != post assign lhs

Acknowledgements

• Thanks to godoc.org for providing a lovely index for scraping bunches of Go.
• Thanks for @kr for github.com/kr/fs, vendored here.
• Thanks to Brad Fitzpatrick for encouraging me to gather this data.