general
Constants hoc_ac_ hoc_cross_y_
float_epsilon hoc_cross_x_ hoc_obj_

predeclared-variables

## SYNTAX

`float_epsilon = 1e-11`

## DESCRIPTION

The default value is 1e-11
Allows somewhat safer logical comparisons and integer truncation for
floating point numbers. Most comparisons are treated as true if they are
within float_epsilon of being true. eg.

execute following example

for (i = 0; i < 1; i += .1) {
print i, int(10*i)
}
float_epsilon = 0
// two bugs due to roundoff
for (i = 0; i < 1; i += .1) {
print i, int(10*i)
}

## BUGS

I certainly haven't gotten every floating comparison in the program to use
float_epsilon but I have most of them including all interpreter logical
operations, int, array indices, and Vector logic methods.

predeclared-variables

A variable used by the graphical interface to communicate with the
interpreter. It is very volatile. It sometimes holds a value on a
function call. If this value is needed by the user it should be
copied to another variable prior to any other function call.

predeclared-variables

## SYNTAX

`hoc_obj_[0]`

`hoc_obj_[1]`

## DESCRIPTION

When a line on a Graph is picked with the PickVector tool
two new Vector 's are created containing the y and x coordinates of the
line. The y vector is referenced by hoc_obj_[0] and the x vector is
referenced by hoc_obj_[1].

predeclared-variables

## SYNTAX

`hoc_cross_x_`

## DESCRIPTION

X coordinate value of the last Crosshair manipulation.
## SEE ALSO

crosshair

predeclared-variables

## DESCRIPTION

Y coordinate value of the last Crosshair manipulation.
## SEE ALSO

crosshair

predeclared-variables

The following mathematical and physical constants are built-in:
"PI", 3.14159265358979323846,
"E", 2.71828182845904523536,
"GAMMA",0.57721566490153286060, /* Euler */
"DEG", 57.29577951308232087680, /* deg/radian */
"PHI", 1.61803398874989484820, /* golden ratio */
"FARADAY", 96484.56, /*coulombs/mole*/
"R", 8.31441, /*molar gas constant, joules/mole/deg-K*/

## BUGS

Constants are not treated specially by the interpreter and
may be changed with assignment statements.
The FARADAY is a bit different than the faraday of the units database.
The faraday in a .mod mechanism is 96520.

neuron/general/predec.hel : May 13 2012