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doc/utils/eval: review and extend, clarify ld/st index meaning

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Prefer idx in place of id for functions accessing the internal
variables, and add a short introduction to mention them.
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Stefano Sabatini 2024-01-05 00:56:40 +01:00
parent 8ceb37d5ad
commit b2bc4ac69e
1 changed files with 33 additions and 27 deletions
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doc/utils.texi
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@ -801,6 +801,11 @@ The following binary operators are available: @code{+}, @code{-},
The following unary operators are available: @code{+}, @code{-}. The following unary operators are available: @code{+}, @code{-}.
Some internal variables can be used to store and load intermediary
results. They can be accessed using the @code{ld} and @code{st}
functions with an index argument varying from 0 to 9 to specify which
internal variable to access.
The following functions are available: The following functions are available:
@table @option @table @option
@item abs(x) @item abs(x)
@ -898,9 +903,9 @@ Return 1.0 if @var{x} is +/-INFINITY, 0.0 otherwise.
@item isnan(x) @item isnan(x)
Return 1.0 if @var{x} is NAN, 0.0 otherwise. Return 1.0 if @var{x} is NAN, 0.0 otherwise.
@item ld(var) @item ld(idx)
Load the value of the internal variable with number Load the value of the internal variable with index @var{idx}, which was
@var{var}, which was previously stored with st(@var{var}, @var{expr}). previously stored with st(@var{idx}, @var{expr}).
The function returns the loaded value. The function returns the loaded value.
@item lerp(x, y, z) @item lerp(x, y, z)
@ -933,16 +938,14 @@ Compute the power of @var{x} elevated @var{y}, it is equivalent to
@item print(t) @item print(t)
@item print(t, l) @item print(t, l)
Print the value of expression @var{t} with loglevel @var{l}. If Print the value of expression @var{t} with loglevel @var{l}. If @var{l} is not
@var{l} is not specified then a default log level is used. specified then a default log level is used.
Returns the value of the expression printed. Return the value of the expression printed.
Prints t with loglevel l
@item random(idx) @item random(idx)
Return a pseudo random value between 0.0 and 1.0. @var{idx} is the Return a pseudo random value between 0.0 and 1.0. @var{idx} is the
index of the internal variable which will be used to save the index of the internal variable used to save the seed/state, which can be
seed/state. previously stored with @code{st(idx)}.
To initialize the seed, you need to store the seed value as a 64-bit To initialize the seed, you need to store the seed value as a 64-bit
unsigned integer in the internal variable with index @var{idx}. unsigned integer in the internal variable with index @var{idx}.
@ -955,8 +958,8 @@ st(0,42); print(random(0)); print(random(0)); print(random(0))
@item randomi(idx, min, max) @item randomi(idx, min, max)
Return a pseudo random value in the interval between @var{min} and Return a pseudo random value in the interval between @var{min} and
@var{max}. @var{idx} is the index of the internal variable which will @var{max}. @var{idx} is the index of the internal variable which will be used to
be used to save the seed/state. save the seed/state, which can be previously stored with @code{st(idx)}.
To initialize the seed, you need to store the seed value as a 64-bit To initialize the seed, you need to store the seed value as a 64-bit
unsigned integer in the internal variable with index @var{idx}. unsigned integer in the internal variable with index @var{idx}.
@ -968,14 +971,14 @@ with argument @var{ld(0)} is 0 in the interval 0..@var{max}.
The expression in @var{expr} must denote a continuous function or the The expression in @var{expr} must denote a continuous function or the
result is undefined. result is undefined.
@var{ld(0)} is used to represent the function input value, which means @var{ld(0)} is used to represent the function input value, which means that the
that the given expression will be evaluated multiple times with given expression will be evaluated multiple times with various input values that
various input values that the expression can access through the expression can access through @code{ld(0)}. When the expression evaluates to
@code{ld(0)}. When the expression evaluates to 0 then the 0 then the corresponding input value will be returned.
corresponding input value will be returned.
@item round(expr) @item round(expr)
Round the value of expression @var{expr} to the nearest integer. For example, "round(1.5)" is "2.0". Round the value of expression @var{expr} to the nearest integer. For example,
"round(1.5)" is "2.0".
@item sgn(x) @item sgn(x)
Compute sign of @var{x}. Compute sign of @var{x}.
@ -993,12 +996,15 @@ Compute the square root of @var{expr}. This is equivalent to
@item squish(x) @item squish(x)
Compute expression @code{1/(1 + exp(4*x))}. Compute expression @code{1/(1 + exp(4*x))}.
@item st(var, expr) @item st(idx, expr)
Store the value of the expression @var{expr} in an internal Store the value of the expression @var{expr} in an internal
variable. @var{var} specifies the number of the variable where to variable. @var{idx} specifies the index of the variable where to store
store the value, and it is a value ranging from 0 to 9. The function the value, and it is a value ranging from 0 to 9. The function returns
returns the value stored in the internal variable. the value stored in the internal variable.
Note, Variables are currently not shared between expressions.
The stored value can be retrieved with @code{ld(var)}.
Note: variables are currently not shared between expressions.
@item tan(x) @item tan(x)
Compute tangent of @var{x}. Compute tangent of @var{x}.
@ -1007,16 +1013,16 @@ Compute tangent of @var{x}.
Compute hyperbolic tangent of @var{x}. Compute hyperbolic tangent of @var{x}.
@item taylor(expr, x) @item taylor(expr, x)
@item taylor(expr, x, id) @item taylor(expr, x, idx)
Evaluate a Taylor series at @var{x}, given an expression representing Evaluate a Taylor series at @var{x}, given an expression representing
the @code{ld(id)}-th derivative of a function at 0. the @code{ld(idx)}-th derivative of a function at 0.
When the series does not converge the result is undefined. When the series does not converge the result is undefined.
@var{ld(id)} is used to represent the derivative order in @var{expr}, @var{ld(idx)} is used to represent the derivative order in @var{expr},
which means that the given expression will be evaluated multiple times which means that the given expression will be evaluated multiple times
with various input values that the expression can access through with various input values that the expression can access through
@code{ld(id)}. If @var{id} is not specified then 0 is assumed. @code{ld(idx)}. If @var{idx} is not specified then 0 is assumed.
Note, when you have the derivatives at y instead of 0, Note, when you have the derivatives at y instead of 0,
@code{taylor(expr, x-y)} can be used. @code{taylor(expr, x-y)} can be used.