List of symbols in the abstract syntax tree of the expression

A list, will be initialized after an instance is built.

Examples

# Constant variable
a <- 1

# Random uniform variable
b <- rand_uniform()

# Define a closed form expression
cf <- closed_form(~3 * (exp(a) + b))

cf
#> 
#> ── <CLOSED_FORM object>
#> EXPR = 3 * (exp(a) + b)
#>  - b: <RAND_UNIFORM object>
#>    [a: 0, b: 1] 

# Get the list of symbols
cf$sym
#> $`*`
#> function (e1, e2)  .Primitive("*")
#> 
#> $`(`
#> .Primitive("(")
#> 
#> $`+`
#> function (e1, e2)  .Primitive("+")
#> 
#> $exp
#> function (x)  .Primitive("exp")
#> 
#> $a
#> [1] 1
#> 
#> $b
#> 
#> ── <RAND_UNIFORM object>
#> [a: 0, b: 1] 
#> 

# Get the list of symbol names
cf$sym_name
#> [[1]]
#> [1] "*"
#> 
#> [[2]]
#> [1] "("
#> 
#> [[3]]
#> [1] "+"
#> 
#> [[4]]
#> [1] "exp"
#> 
#> [[5]]
#> [1] "a"
#> 
#> [[6]]
#> [1] "b"
#> 

# Get the list of symbol types
cf$sym_type
#> $`*`
#> [1] "other"
#> 
#> $`(`
#> [1] "other"
#> 
#> $`+`
#> [1] "other"
#> 
#> $exp
#> [1] "other"
#> 
#> $a
#> [1] "other"
#> 
#> $b
#> [1] "rand_var or closed_form"
#> 

d <- rand_normal()

# Define a closed form expression with another closed form expression
cf2 <- closed_form(~cf + 3 * d)

cf2
#> 
#> ── <CLOSED_FORM object>
#> EXPR = cf + 3 * d
#>  - cf: <CLOSED_FORM object>
#>    EXPR = 3 * (exp(a) + b)
#>     - b: <RAND_UNIFORM object>
#>       [a: 0, b: 1]
#>  - d: <RAND_NORMAL object>
#>    [mu: 0, sigma: 1] 

# Get the list of symbols, constants are not counted as symbols
cf2$sym
#> $`+`
#> function (e1, e2)  .Primitive("+")
#> 
#> $cf
#> 
#> ── <CLOSED_FORM object>
#> EXPR = 3 * (exp(a) + b)
#>  - b: <RAND_UNIFORM object>
#>    [a: 0, b: 1] 
#> 
#> $`*`
#> function (e1, e2)  .Primitive("*")
#> 
#> $d
#> 
#> ── <RAND_NORMAL object>
#> [mu: 0, sigma: 1] 
#> 

# Get the list of symbol names
cf2$sym_name
#> [[1]]
#> [1] "+"
#> 
#> [[2]]
#> [1] "cf"
#> 
#> [[3]]
#> [1] "*"
#> 
#> [[4]]
#> [1] "d"
#> 

# Get the list of symbol types
cf$sym_type
#> $`*`
#> [1] "other"
#> 
#> $`(`
#> [1] "other"
#> 
#> $`+`
#> [1] "other"
#> 
#> $exp
#> [1] "other"
#> 
#> $a
#> [1] "other"
#> 
#> $b
#> [1] "rand_var or closed_form"
#>