;+
;procedure:  thm_crib_calc.pro
;
;purpose: demonstrate how to use the mini-language program 'calc'
;
;usage:
; .run thm_crib_fgm
;
;
; $LastChangedBy: pcruce $
; $LastChangedDate: 2008-09-15 17:05:42 -0700 (Mon, 15 Sep 2008) $
; $LastChangedRevision: 3501 $
; $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/thmsoc/tags/tdas_8_00/idl/themis/examples/thm_crib_calc.pro $
;
;-


;the mini-language is a language written in IDL that can be run on the
;idl virtual machine.  It follows most of the syntactical rules of IDL
;with the exception that tplot variables are treated as first-class
;data types in the mini-language.  They are denoted with "quotes" the
;same way that you would denote strings in normal IDL.
;All statements in the mini-language must be assignment statements 
;(ie variable = expression)


;Example 1 var = number

;sets a equal to 5
calc,'a = 5'

stop

;Example 2 binary operation.

;This performs multiplication on "b", you can use any of the idl
;operators with calc
b = 7
calc,'seven_pi = b * 3.14159'

stop

;Example 3 function/exponential notation

;This performs a function call. Also note that calc can read the same
;numerical format code as IDL.  The default type, if unspecified is a
;float rather than a short int, as floats are much more common in
;scientific applications
calc,'log_result = log(1e-2)'  ;log base 10

calc,'log_result = ln(1e-2)' ; log base e

stop

;Example 4 tvar = number

;creates a tplot variable named 'a' with the y component of its data
;struct equal to 5.  Because the number 5 doesn't have any
;associated time information, neither will "a"
calc,'"a"=5'

stop

;Example 5 real tvar

;load some real data
timespan,'2007-03-23'
thm_load_state,probe='a'

;performs division on tplot variable
;Note that calc does not yet accept globbing operators
; like '?' and '*', so 'th?_state_pos' is currently an invalid name.
;We plan to add this feature soon.

calc,"'tha_pos_re' = 'tha_state_pos'/6374.4"

stop

;example 6 combined tvar/var

;you can combine normal and tplot variables in the same expression
dpi = !DPI
calc,'"tha_pos_sin" = sin("tha_pos_re"*dpi)'

stop

;example 7 getting tvar data with cacl

;you can use calc as an easy way to read the data component of a tplot
;variable, after this call, data will have the data component of tha_state_pos

calc,'data = "tha_state_pos"'

stop

;example 8 order of operation

;calc follows the same order of operations
;and numerical type codes as IDL.  If unspecified,
;the default type is float(not short int like IDL)
calc,'out = 5.1 + 6.02e-3 ^ 2b * 7.6D'

stop

;example 9 errors

;note that calc does not report errors by stopping execution or
;printing to the command line.  If an error occurs, it returns a
;struct describing this error in a keyword called 'error'

calc,'out = "?%3"',error=e

help,/str,e
print,e.value

stop

;example 10 verbose

;you can use the /verbose option to print the error rather than return the struct
calc,'out= "?%3"',/verbose

stop

;example 11 function and operator lists

;calc will return a list all the available functions and operators

calc,function_list=f,operator_list=o

print,'Functions: ',f
print,'Operators: ',o

stop

;example 12 multi argument functions

;some functions take multiple arguments
;a second argument to 'log', is an alternate base
;also note that 'ln' is a base e logarithm

calc,'log_2 = log(64,2)'

stop

;example 13 more multi argument functions

;some functions take the dimension over which the operation
;should be performed

calc,'t = total("tha_state_pos")' ;total over all dimensions
;t is 1 element

calc,'t = total("tha_state_pos",1)' ; total over time
;t is 3 elements

calc,'t = total("tha_state_pos",2)' ; total over x,y,z
;t is 1440 elements

stop

;example 14 exp

;exp also takes a base as an optional argument. 

calc,'ex = exp(2)'  ; ex = e^2

calc,'ex = exp(6,2)' ; ex = 2^6 = 64.0

calc,'ex = exp(log(64,2),2)' ; ex = 2^log_2(64) = 64

stop

end