Optimizer: Common Subexpression Elimination. — opt_common

Performs one common subexpression elimination pass. Carefully examine the results after running this function!

opt_common_subexpr(texts, n_values = 2, in_fun_call = FALSE)

Arguments

texts	A list of character vectors with the code to optimize.
n_values	A numeric indicating the minimum number of values to consider a subexpression.
in_fun_call	A logical indicating whether it should propagate in function calls. Note: this could change the semantics of the program.

Examples

code <- paste(
  "a <- b * c + g",
  "d = b * c * e",
  sep = "\n"
)
cat(opt_common_subexpr(list(code))$codes[[1]])
#> cs_1 <- b * c
#> a <- cs_1 + g
#> d = cs_1 * e

heron_formula <- paste(
  "area <- (a/2 + b/2 +c/2) * (a/2 + b/2 + c/2 - a) * (a/2 + b/2 + c/2 - b) *",
  "  (a/2 + b/2 + c/2 - c)",
  "area <- sqrt(area)",
  sep = '\n'
)
cat(opt_common_subexpr(list(heron_formula))$codes[[1]])
#> cs_1 <- a/2 + b/2 +c/2
#> area <- (cs_1) * (cs_1 - a) * (cs_1 - b) *
#>   (cs_1 - c)
#> area <- sqrt(area)