Working out a reporting challenge from HN, part 1. See also part 2 (foreign exchange gains): https://gist.github.com/simonmichael/28f94ce2bd73318e4fccbfa7c9fc7e87

avodonosov-example.journal

; avodonosov problem, from https://news.ycombinator.com/item?id=28424432
; For example
; Jan 1
;   Received 1000 EUR for a contract
;   The rate 1 EUR = 2 BYN
; Jan 2
;   Exchanged 300 EUR to BYN
;   The rate 1 EUR = 2.1 BYN
; Jan 3
;   Received 2000 EUR for a contract
;   The rate 1 EUR = 2.2 BYN
; Jan 5
;   Exchanged 600 EUR to BYN
;   The rate 1 EUR = 2.3 BYN
; Jan 30:
;   The rate 1 EUR = 2.5 BYN
; I need reports net worth, total income for the month, capital gains.
; First generate the report in BYN, then in EUR, then in USD. 
; Let's assume the commissions are zero.
; Net worth is easy - current sum in original currencies and then convert to the currency of the report using the current rate
; But what ledger was failing to do, for me, is to compute capital gains.
; And, as I remember, it was unable to even balance the ledger
; How would one describe this use case in ledger format?

1/1
    revenues                                   -1000 EUR
    assets:eur                                  1000 EUR

P 1/1 EUR 2 BYN

1/2
    assets:eur                                  -300 EUR @ 2.1 BYN
    assets:byn                                   630 BYN

1/3
    revenues                                   -2000 EUR
    assets:eur                                  2000 EUR

P 1/3 EUR 2.2 BYN

1/5
    assets:eur                                  -600 EUR @ 2.3 BYN
    assets:byn                                  1380 BYN

P 1/30 EUR 2.5 BYN
P 1/30 EUR 1.21 USD

reports

#!/usr/bin/env bash

export LEDGER_FILE=avodonosov-example.journal

echo "First generate the report in BYN, then in EUR, then in USD."
echo "Net worth, valued at month end"
echo
hledger bs; echo
hledger bs -X BYN; echo
hledger bs -X EUR; echo
hledger bs -X USD; echo
echo
echo
echo "Total income for the month, valued when received"
echo
hledger is -M; echo
hledger is -M --value=then,BYN; echo
hledger is -M --value=then,EUR; echo
hledger is -M --value=then,USD; echo

z-output.shell

First generate the report in BYN, then in EUR, then in USD.
Net worth, valued at month end

Balance Sheet 2021-01-05

             ||           2021-01-05 
=============++======================
 Assets      ||                      
-------------++----------------------
 assets:byn  ||           2010.0 BYN 
 assets:eur  ||             2100 EUR 
-------------++----------------------
             || 2010.0 BYN, 2100 EUR 
=============++======================
 Liabilities ||                      
-------------++----------------------
-------------++----------------------
             ||                      
=============++======================
 Net:        || 2010.0 BYN, 2100 EUR 

Balance Sheet 2021-01-30, valued at period ends

             || 2021-01-30 
=============++============
 Assets      ||            
-------------++------------
 assets:byn  || 2010.0 BYN 
 assets:eur  || 5250.0 BYN 
-------------++------------
             || 7260.0 BYN 
=============++============
 Liabilities ||            
-------------++------------
-------------++------------
             ||            
=============++============
 Net:        || 7260.0 BYN 

Balance Sheet 2021-01-30, valued at period ends

             || 2021-01-30 
=============++============
 Assets      ||            
-------------++------------
 assets:byn  ||    804 EUR 
 assets:eur  ||   2100 EUR 
-------------++------------
             ||   2904 EUR 
=============++============
 Liabilities ||            
-------------++------------
-------------++------------
             ||            
=============++============
 Net:        ||   2904 EUR 

Balance Sheet 2021-01-30, valued at period ends

             ||  2021-01-30 
=============++=============
 Assets      ||             
-------------++-------------
 assets:byn  ||  972.84 USD 
 assets:eur  || 2541.00 USD 
-------------++-------------
             || 3513.84 USD 
=============++=============
 Liabilities ||             
-------------++-------------
-------------++-------------
             ||             
=============++=============
 Net:        || 3513.84 USD 



Total income for the month, valued when received

Income Statement 2021-01

          ||      Jan 
==========++==========
 Revenues ||          
----------++----------
 revenues || 3000 EUR 
----------++----------
          || 3000 EUR 
==========++==========
 Expenses ||          
----------++----------
----------++----------
          ||          
==========++==========
 Net:     || 3000 EUR 

Income Statement 2021-01, valued at posting date

          ||        Jan 
==========++============
 Revenues ||            
----------++------------
 revenues || 6400.0 BYN 
----------++------------
          || 6400.0 BYN 
==========++============
 Expenses ||            
----------++------------
----------++------------
          ||            
==========++============
 Net:     || 6400.0 BYN 

Income Statement 2021-01, valued at posting date

          ||      Jan 
==========++==========
 Revenues ||          
----------++----------
 revenues || 3000 EUR 
----------++----------
          || 3000 EUR 
==========++==========
 Expenses ||          
----------++----------
----------++----------
          ||          
==========++==========
 Net:     || 3000 EUR 

Income Statement 2021-01, valued at posting date

          ||      Jan 
==========++==========
 Revenues ||          
----------++----------
 revenues || 3000 EUR 
----------++----------
          || 3000 EUR 
==========++==========
 Expenses ||          
----------++----------
----------++----------
          ||          
==========++==========
 Net:     || 3000 EUR